Amazon has announced two new Java-based applications for Windows and Mac PCs that will sync files between multiple computers and the company's Cloud Drive online storage service.

Amazon Cloud Drive is a companion service that was spun off of its Cloud Player music locker service. Users get 5GB for free, with additional tiers of storage available for purchase. (Any music from Amazon side-loaded to Cloud Drive and Cloud Player before July 31st does not count towards your storage quota). Until now, Cloud Drive has been merely a web storage locker, but with the new desktop apps Amazon is adding file syncing capabilities that will keep your files updated across multiple PCs. The desktop apps will create a folder which will then contain a locally-stored copy of your Amazon Cloud Drive files. If you choose to install the desktop app onto a second PC, it will also sync with Cloud Drive and store a copy of the files locally. The most recently modified version will sync to all the other computers' local store and the cloud drive. There is no word on versioning support, so note that this should not be a replacement for a true file backup. With that said, the multiple-PC file sync is a welcome addition that makes Cloud Drive much more useful than ever before.

The new desktop apps will run on Windows XP, Vista, 7, and 8, and on Mac OS X 10.6, 10.7, and 10.8.

When Amazon was asked about mobile apps and file sync, the company told Ars Technica that it had "nothing specific to share." That could mean that Cloud Drive will bring file synchronization to iOS, Android, and WP8, or it could be a literal statement. It is difficult to say, but I think if Amazon wants its Cloud Drive storage service to be taken seriously the company will need to enter the mobile space (as it has done with Cloud Player).

Read more about cloud storage at PC Perspective, including a review of Google Drive and a look at the new SkyDrive.